A computer program helps integrate the information from individual sequencing reactions. It spots where fragments overlap, to puzzle the pieces back together.
Many overlapping sequencing reads are needed to reveal the uninterrupted sequence of the original stretch of DNA. On average, every base pair of human DNA will be sequenced nine times. Some stretches of DNA are easier to read and need to be sequenced a little less often to get high-quality sequence. Some stretches need to be analyzed more exhaustively to get finished high-quality sequence.
To sequence the human genome, scientists will ultimately run more than 50 million reactions. Some 2000 scientists, in more than 2 dozen labs around the world, have worked toward the goal.
Human Genome Research Institute